The statistics of the Weapon are what make it arguably the best weapon. Look at the stats in the UESP
My character does look like she needs to eat more.

IIRC the speed info is wrong as I think I recall hearing that greatswords are no faster than axes. In Morrowind while skills were still branched in Blunt and Axe they had bonus on Axes, so that's as far as you'll get about what would suit them better lore wise.
Gameplay wise as you know swords are best at critical damaging, axes cause bleeding and hammers ignore armor.

Hope this helped.

EDIT: as for the best Uniqes Volendrung takes the 1st place by far- hammer with base damage of 25 (the highest you'll find) and absorbs 50 stamina which means you can practically use charge attacks constantly. It also has the exact same attack speed as greatsword so you get nothing by using a sword instead of this hammer.

Hmm..i have readed what the stats says -even if i don't mind them too much,i wouldn't use hammer neither under torture - but you've not readed well my joke perhaps

p.s. its simply referred to the searching for "logical reasons" that seems to emerge too frequently here sometimes -and have even one of my "usual metaphor" in - try to find it ...

I'd go for a battleaxe, but this is purely based on looks. I have no idea how the stats of 2h weapons line up.

What is your personal favorite then?

Well only if he'll be enchanting. In that case both Ebony and Daedric can be better.

I'm a swordsman myself. I prefer launching a ruthless and unrelenting assault with two swords until either their shields break, or they break.